1. Field of the Invention
The present invention relates to a three-dimensional image capturing device by which a three-dimensional shape of a measurement subject, which is to be measured, is captured by a time-of-flight measurement and its laser for emitting a measurement light beam.
2. Description of the Related Art
A three-dimensional measurement using a three-dimensional image capturing device is classified as an active system, in which light, an electric wave or sound is radiated onto a measurement subject, and a passive system in which the light, electric wave or sound is not output. The active system comprises the time-of-flight measurement, a phase detection using a modulated light wave, a triangulation, a moirxc3xa9 topography, and so on, and the passive system comprises a stereo vision system, and so on.
An active system device is bulky in comparison with that of the passive system, since the device requires a laser beam output mechanism. However, the active system device is superior regarding a distance measurement resolution, a measuring time, a measuring range and so on, and thus, despite the bulkiness, the device is utilized in various fields. In a three-dimensional image capturing device, described in xe2x80x9cMeasurement Science and Technologyxe2x80x9d (S. Christies et al., vol.6, p.1301-1308, 1995), a pulse-modulated laser beam irradiates a whole of a measurement subject through an illumination lens, and a reflected light beam, which is reflected by the measurement subject, is received by a two-dimensional CCD sensor to which an image intensifier is attached, so that an image signal, corresponding to the reflected light beam, is converted to an electric signal. ON-OFF control of the image intensifier is carried out by a gate pulse, which is synchronized with the pulse radiation of the laser beam. According to the device, since an amount of received light, based on the reflected light beam from the measurement subject, which is positioned far from the device, is less than that of received light based on a reflected light beam from a measurement subject, which is close to the measurement subject, an output corresponding to a distance between the measurement subject and the device can be obtained for each pixel of the CCD.
However, if a person is standing nearby the measurement subject and is in the range of the divergent laser illumination, a laser beam may become incident on an eye of the person and may damage the retina. Therefore, three-dimensional measurement using laser beam may be harmful to the retina of a bystander during the measurement.
An object of the present invention is to provide a three-dimensional image capturing device and its laser emitting device which emits a laser beam onto a measurement subject to detect three-dimensional distance information of the subject without causing retina damage to an eye of a bystander.
According to the present invention, there is provided a laser emitting device applied in a three-dimensional image capturing device, comprising a plurality of laser devices and a laser emitting operating processor.
The plurality of laser devices radiates pulse modulated laser beams irradiating a measurement subject for a distance measurement, and the plurality of laser devices is separated into predetermined groups. The laser emitting operating processor controls the laser devices to radiate laser beams concurrently in a group. Each of the laser devices in each group is disposed at predetermined intervals. Further, each illuminating area of the laser beam radiated from each laser device overlaps each other at the distance of the measurement subject.
In a preferable example of the laser emitting device, the plurality of laser devices is disposed at regular intervals along a periphery of a photographing lens in a circular arrangement. In another preferable example, a plurality of laser devices is arranged at regular intervals along a line in a predetermined direction.
Further, according to the present invention, there is provided a three-dimensional image capturing device, comprising a plurality of laser devices, an imaging device, a signal charge accumulation control processor, a signal charge accumulation control processor, a signal charge integrating processor and a laser emitting operating processor.
The plurality of laser devices radiates pulse modulated laser beams irradiating a measurement subject for a distance measurement, and the plurality of laser devices is separated into predetermined groups. The imaging device accumulates signal charge corresponding to a quantity of light received at the imaging device. The signal charge accumulation control processor controls an accumulating operation of signal charge generated in the imaging device due to a reflected light beam of the laser beam, which is reflected by the measurement subject. The signal charge integrating processor drives the signal charge accumulation control processor repeatedly, so that the signal charge accumulated in the imaging device is integrated. The laser emitting operating processor controls the laser devices, which radiate laser beams concurrently in said group. Each of the laser devices in each group is disposed at predetermined intervals. Further, each illuminating area of the laser beam radiated from each laser device overlaps each other at the distance of the measurement subject.
Further, according to another aspect of the present invention, there is provided a three-dimensional image capturing device, comprising a plurality of laser devices, an imaging device and a laser radiating control processor.
The plurality of laser devices radiates pulse modulated laser beams for a distance measurement in order to detect distance information related to the topography of a measurement subject. The imaging device accumulates signal charge corresponding to a quantity of light received at the imaging device. The laser radiating control processor controls the plurality of laser devices to radiate the laser beams in a predetermined order. Further, each of the laser devices is disposed at predetermined intervals and each illuminating area of said laser beam radiated from each laser device overlaps each other at the distance of the measurement subject.
Preferably, the device further comprises a signal charge accumulation control processor and a signal charge integrating processor. The signal charge accumulation control processor controls an accumulating operation of signal charge generated in the imaging device due to a reflected light beam of the laser beam, which is reflected by the measurement subject. The signal charge integrating processor drives the signal charge accumulation control processor repeatedly, so that the signal charge accumulated in the imaging device is integrated. The laser radiating control processor controls the plurality of laser devices to radiate the reflected light beams successively and alternately, so that each of said laser beams may be received respectively in each of accumulating operations executed in the signal charge integrating processor.
Further, the imaging device preferably comprises a plurality of photoelectric conversion elements and a signal charge holding unit. The plurality of photoelectric conversion elements accumulates the signal charge in each of the photoelectric conversion elements, and the signal charge holding unit is disposed adjacent to each of the photoelectric conversion elements. So that, the signal charge accumulated in each of the photoelectric charge conversion elements is transferred to each of said accumulating operations executed in the signal charge integrating processor.
Furthermore, the plurality of laser devices may be disposed at regular intervals along a periphery of a photographing lens in a circular arrangement, and the laser radiating control processor controls each of the laser devices so as to radiate the laser beams from each of the laser devices successively around the circular arrangement. Alternatively, the plurality of laser devices may be arranged at regular intervals along a line in a predetermined direction and the laser devices repeatedly radiate the laser beams successively along the line.
In another preferable example of the three-dimensional image capturing device, the laser radiating control processor controls the plurality of laser devices to radiate the laser beams in a predetermined order consecutively, so that the consecutive laser beams compose a single pulse beam for the distance measurement, and preferably, the single pulse beam comprises a rectangular pulse.
In this example, the laser beams may be radiated from the plurality of laser devices successively along the arrangement so as to compose the single pulse beam. The imaging device receives a reflected light beam of the single pulse beam, and detects the distance information, which relates to the measurement subject, from signal charge accumulated in the imaging device, due to the single pulse beam, during a predetermined period.
Further, the laser radiating control processor is driven repeatedly and the imaging device respectively accumulates the signal charge in each of the predetermined periods that corresponds to each of said single pulse beams. Moreover, if the imaging device is comprised of the plurality of photoelectric conversion elements and the signal charge holding unit, the signal charge accumulated in each of the photoelectric conversion elements may be transferred to each of the corresponding signal charge holding units for each of the predetermined periods.